1. Field of the Invention
The present invention relates to an optical component used for a laser marker and the like. The present invention specifically relates to a laser line-generator that converts a point light source of laser light to a line light source, and a laser line-generator module that integrates the laser-line generator with a laser light source.
2. Description of the Related Art
A straight line generated by a laser line-generator using a conventional cylindrical lens has a characteristic that the both end portions are darker than the bright central portion. Therefore, in a reference setting operation of providing a long reference line, the both ends are difficult to see, which causes a decrease in workability. FIG. 10 is a principle diagram of a laser-line generator using a semi-cylindrical rod lens. A semi-cylindrical rod lens MR having a radius R is set with an optical axis Z as a central axis, and a screen S is placed at a predetermined distance in parallel with an entrance boundary surface of the semi-cylindrical rod lens MR. Incoming light L1 by a laser parallel beam is incident on the entrance boundary surface 10 in parallel with the optical axis Z, and outgoing light L2 refracted on an exit surface 20 draws a straight line on the screen S.
The incoming light L1 is incident at an incidence angle θ1 with respect to a normal line P to the exit surface, and becomes the outgoing light L2 as a result of being refracted at a refraction angle θ2. The incidence angle θ1 of the incoming light L1 is small near the optical axis Z, and increases as the incoming light L1 becomes away from the optical axis Z and a distance X between the optical axis Z and the incoming light L1 approaches the radius R. This being so, the refraction angle θ2 of the incoming light L1 incident near the optical axis Z is small, and the outgoing light L2 draws a bright straight line without much dispersion. However, as the incoming light L1 becomes away from the optical axis Z and the distance X increases, the incidence angle θ1 rapidly increases, and the refraction angle θ2 increases too, so that the incoming light L1 is greatly refracted. This causes large dispersion of the outgoing light L2, and the interval between adjacent outgoing light beams widens and an outgoing light density drops. As a result, a dark straight line is drawn.
FIG. 11 is a luminance characteristics chart showing a relation between straight line brightness and a deflection angle (W=θ2−θ1) formed by the outgoing light with the optical axis. In a deflection angle curve D, the deflection angle W rapidly increases as the incoming light L1 becomes away from the optical axis Z and the distance X between the incoming light L1 and the optical axis Z approaches the distance of the radius R. The curve stops at the point of the deflection angle W where total reflection occurs. A luminance curve B varies in accordance with this deflection angle curve D, in such a manner that the luminance is highest when the incoming light L1 is on the optical axis Z and decreases as the distance X approaches the distance of the radius R. FIG. 12 is a straight line drawing schematic view schematically showing straight line drawing. The incoming light L1 enters the semi-cylindrical lens MR, and the outgoing light L2 greatly disperses at the both ends and decreases in light quantity, so that a straight line with the both end portions darker than the central portion is generated. Japanese Patent Application Laid-Open No. 2003-329454 describes a mechanism of automatically correcting vertical and horizontal line light emission positions of a laser marker that includes a laser light source, a collimating lens, and a cylindrical lens.